Muffler and outlet tube for small internal combustion engines



April 16, 1968 D. GORDON 3,378,099

MUFFLER AND OUTLET TUBE FOR SMALL INTERNAL COMBUSTION ENGINES FiledSept. 15, 1967 2 Sheets-Sheet l Snack/44%;

35 {Quakes Simian i 1%,,

April 16, 1968 D. GORDON 3,378,099

MUFFLER AND OUTLET TUBE FOR SMALL INTERNAL COMBUSTION ENGINES FiledSept. 15, 1967 2 Sheets-Sheet 2 f I .3. i

SPOT WELDED SPOT WELDED United States Patent 01 fee 3 378 099 MUFFLERAND OUTLET TUBE FGR SMALL INTERNAL COMBUSTIQN ENGENES Douglas Gordon,Hartford, Wis, assignor to Briggs &

Stratton Corporation, Wauwatosa, Wis, a corporation of Delaware FiledSept. 15, 1967, Ser. No. 667,914 11 Claims. (Cl. 181-40) ABSTRACT OF THEDISCLOSURE An outlet tube from which engine exhaust gas is discharged ina desired direction has a fiat elongated balfle plate in its downstreamportion which cooperates with the tube to define two passages, onegenerally convergent downstream and the other generally divergent. Thewall portion of the tube that defines the divergent passage has a largenotch opening .to its discharge end. The downstream portion of thebafiie plate has lengthwise elongated apertures.

This invention relates to exhaust mufilers for internal combustionengines and refers more particularly to a muffling outlet tube that isespecially adapted for use on single cylinder engines and by whichexhaust gases issuing from the engine are caused to be discharged in adesired direction and to a desired zone or location near the body of theengine.

In many small engine installations, and particularly on small ridingtractors and riding mowers, it is highly desirable to provide fordischarge of engine exhaust gases in a desired direction or to someparticular zone near the engine body, in order to avoid the possibilityof having a concentrated stream of exhaust gases blown against a personstanding near the engine or against delicate plants or the like nearwhich the engine is moved. in many cases it is desirable that theexhaust gases be discharged in a direction generally opposite to that inwhich they leave the engine body. Thus, if an exhaust port is located atone side of an engine cylinder body, the desired outlet would direct theemergent gases generally back across or over the cylinder body orcylinder head.

-In most cases the provision of a plain outlet tube on the muffler of asmall engine for effecting such controlled discharge of exhaust gasesresults in a substantial increase in exhaust noise so that the exhausttube actually cancels some of the silencing effects of the muffler.

An example of the noise augmenting effect of a plain outlet tube isprovided by experience with a muffler similar to that disclosed inPatent No. 3,168,936, issued Feb. 9, 1965 to Douglas Gordon. The mufllerof that patent had an expansion chamber comprising a pair of relativelyshallow and generally rectangular pan-like shell members, with 'bafiiemeans in its interior. It had an inlet port in its rear wall and had anoutlet deflector at its front that was adjustable to cause exhaust gasesto be discharged either parallel to the direction in which they flowedinto the expansion chamber or in substantially any direction at rightangles to the direction of entry. When used with its regular outlet,that muffler provided very satisfactory silencing.

However, an attempt was made to adapt that mufiier for so-called reverseflow, whereby the exhaust gases would be caused to undergo about a 180change of direction in the course of flow through the mutiier.

To this end an outlet port was provided in the rear of the expansionchamber, instead of at its front, and a plain outlet tube was fastenedto its rear, in register with the outlet port, to conduct exhaust gasespartway back across the cylinder to a discharge zone alongside thecylinder 3,378,999 Patented Apr. 16, 1968 head. It was found that themuflier so modified was substantially more noisy than in its originalform as disclosed in Patent No. 3,168,936, and that the outlet tube wasresponsible for the higher noise level.

With the foregoing comments in mind, it is a general object of thisinventioin to provide a mufi'ler outlet tube for small single cylinderengines whereby engine exhaust gases can be discharged'in a desireddirection and to a desired zone, which outlet tube does not increase thenoise level of the mufiier.

Another object of this invention is to provide a mufiier generallysimilar to that of Patent No. 3,168,936, but from which exhaust gasesare discharged in a direction generally opposite to that of their entryinto the Inufiler and having an outlet tube from which exhaust gases canbe discharged at a distance from the rnuflier body and which providesgood muflling without absorbing an undue amount of engine power.

Another specific object of this invention is to provide an exhaustmufiier outlet tube of the character described that is readilyadjustable to some extent to enable its discharge end portion to be setin any of a number of different positions that will accommodate variousinstallation conditions and situations.

With these observations and objects in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings. This disclosure is intendedmerely to exemplify the invention. The invention is not limited to theparticular structure disclosed, and changes can be made therein whichlie within the scope of the appended claims without departing from theinvention.

The drawings illustrate one complete example of the physical embodimentof the invention constructed according to the best mode so far devisedfor the practical application of the principles thereof, and in which:

FIGURE 1 is a fragmentary perspective view of a portion of a singlecylinder engine on which there is installed an exhaust rnufilerembodying the principles of this invention;

FIGURE 2 is a view in rear elevation of the muffler itself, withportions shown broken away;

FIGURE 3 is a sectional view taken on the plane of the line 3-3 inFIGURE 2; and

FIGURE 4 is a fragmentary sectional view through the outlet tube, takenon the plane of the line 44 in FIGURE 3.

Referring now more particularly to the accompanying drawings, thenumeral 4 designates generally the cylinder portion of a single cylinderengine having an exhaust mutiler 5 fastened to one side thereof so thatan inlet opening 6 in the rear of the rnufiier is in register with anexhaust port 7 in the side of the cylinder body. Exhaust gases enteringthe mufiier 5 from the exhaust port 7 undergo a substantially completereversal of direction in the course of flow therethrough and aredischarged to a zone generally near the cylinder head and about halfwayacross it from a rearwardly projecting outlet tube 8 on the mufiier thatembodies the principles of this invention.

The mufiler comprises complementary front and rear pan-like shellmembers 10 and 11 that cooperate to define an expansion chamber 12.Within the expansion chamber are an inlet bafile 13 that also performs astructure supporting function described hereinafter, and a second baffle14. There is also a baffle 15 in the outlet tube 8.

The front shell member 10 has a rim 16 around its edge that is clinchedaround a flange-like rim 17 on the rear shell member 11 to hold theshell members assembled. The expansion chamber, as viewed from the frontor the rear thereof, is generally rectangular in outline, but hasrounded corners. The inlet opening 6 is formed in the rear shell member,near one corner thereof, and is adapted to register with an exhaust port7 in the side of an engine cylinder body. Near its opposite corner therear shell member has an outlet opening 19 with which the outlet tube 8registers.

The rear wall of the rear shell member comprises two wall portions 20and 21 that are obliquely inclined to one another at an obtuse angle.The wall portion 20' in which the inlet opening 6 is formed is generallyperpendicular to the side walls of the expansion chamber and parallel toits front wall. The other wall portion 21, in which the outlet opening1? is formed, slopes forwardly and toward the corner nearest the outletopening.

The muffler can be secured to an engine body by means of bolts 22extending through coaxially aligned holes in the front and rear walls ofthe expansion chamber and received in threaded holes in the cylinder.The inlet baffle 13, which extends edgewise between the front and rearwalls of the expansion chamber, substantially parallel to the axis ofthe inlet opening, supports those walls against the converging forcesthat the bolts 22 exert upon them as the bolts are tightened, and asmall plate 24 through which both bolts pass overlies the front wall todistribute those forces. If desired, a heat shield plate 25 can beinterposed between the rear wall of the expansion chamber and thecylinder to afford protection to a fuel line 26 or other part thatshould not be subjected to high heat.

The inlet bafile 13 is generally similar to that of Patent No.3,168,936, comprising a tube bent from a fiat blank to a general diamondshaped cross section but with rounded corners, and having numerousperforations. A portion of the rear wall of the expansion chamber aroundthe inlet opening 6 is slightly dished, as at 27, to receive the rearend of the inlet baffle with a close nesting fit, for steadying thebattle during assembly of the unit. The inlet bailie is further heldagainst lateral shifting by the bolts 22, which extend along its remoteinner corners.

The inlet bafiie is bent in such a way that its adjacent edges areslightly spaced apart, as at 28, and is so mounted that the said edgesare nearest the adjacent corner of the expansion chamber. Its wallportions bounded by the edges just mentioned have substantially shallownotches 29 that open to said edges and to the front edge of the baffle,and the opposite wall of the battle has a substantially deep notch 30opening to its front edge. It will be seen that the inlet baffle 13defines a tortuous flow path for gases entering the expansion chamber,whereby such gases are divided into divergent streams that are caused toflow through the expansion chamber toward the outlet opening 19 alongpaths of unequal length.

Before entering the outlet opening, however, the gases must traverse afurther tortuous path defined by the second bafiie I1 4. The secondbafile can be formed from a single piece of sheet material to have twomain wall portions 3'1 and 32 that are at an obtuse angle to oneanother, both provided with numerous perforations. The larger wallportion 31 is disposed parallel to the front and re'ar walls of theexpansion chamber, behind the inlet opening and about on the plane ofthe shell rims. The portion 33 of the front wall of the expansionchamber that lies in front of said Wall portion 301. of the secondbafile is stepped or rearwardly offset with respect to the remainder ofthe expansion chamber front wall to cobperate with the baffle wallportion 31 in defining a relatively narrow passage from which exhaustgases must pass through the perforations in the second baffle to reachthe outlet opening 19.

The other wall portion 32 of the second baffle extends obliquelyrearwardly and toward the inlet opening, and has its edges closelyadjacent to the side and rear walls, respectively, of the rear shellmember. Legs 34 that extend forwardly fro-m the free edges of the largerwall portion 31 underlie the side walls of the front shell member andare spot welded thereto to hold the second baffie in place. It will beseen that the second baffle extends across the expansion chamber in sucha manner that it must be traversed by all gases flowing from the inletopening 6 to the outlet opening 19.

The outlet tube 8 has a small bend 35 in its medial portion to disposeits opposite end portions at an obtuse angle to one another. This angleis complementary to the angle between the rear wall portions 20 and 21of the expansion chamber so that in one rotational position of theoutlet tube the axis of its downstream or rear end portion can beparallel to the axis of the expansion chamber inlet opening. Near itsfront end the tube has a radially outwardly projecting circumferentialflange 36 that can be defined by a crimp, and the front end portion ofthe tube is receivable in the outlet opening 19 with this flangeoverlying the rear wall portion 2 1 of the expansion chamber.

Overlying the flange 36 is a plate 37 in which there is a hole thatclosely fits around the tube, and said plate is secured to the wallportion 21, as by means of sheet metal screws 37, to cooperate with theflange 36 in holding the tube in place. It will be observed thatloosening of the sheet metal screws 37 allows the tube to be adjustinglyswiveled to accommodate it to a variety of different installationconditions and circumstances.

A plain tube or duct secured to the expansion chamber to direct gasesrear-wardly in the maner of the tube 8 would actually intensify theexhaust noise of the engine, partially cancelling the silencing effectsof the expansion chamber. However, the outlet tube 8 of this inventionhas in it the bafiie 15 which cooperates with the tube to define a pairof laterally adjacent passages 38 and 39, one of which is effectivelyshorter than the other, said baflie providing a wall common to those twopassages and which is apertured at its downstream end to permitcommunication between the passages. With the arrangement of thisinvention the outlet 8 does not diminish the silencing effects of theexpansion chamber and causes no appreciable diminution of engine poweroutput.

The baffie 15, which is flat and rectangular, extends lengthwise in theoutlet tube and has its upstream end a little forward of the bend 35 inthe tube while its downstream end is flush with the rear end of thetube. Transversely the baffle 15 extends substantially all the wayacross the tube and has its opposite edges spot welded to the wall ofthe tube at lengthwise spaced locations. The baffle thus cooperates withthe tube in defining the pair of p'a's's'ages 38 and 39 therein.

The faces of the baiile are perpendicular to the plane that contains theaxes of the obliquely angled end portions of the tube, and the baffle isso disposed in the tube as to have its faces at acute angles to both ofthose axes; hence the passages 6b and 39 are of changingcross-section-a1 areas along their lengths, the passage 38 being ofgenerally diminishing cross sectional area along the direction of gasflow and the passage 39 being of generally increasing cross-sectionalarea along said direction. Further to increase the effectivecross-sectional area of the downstream end portion of the passage 39,the tube has a substantially large notch 42 opening to its rear end, atthe side of the tube that defines the passage 39 and opposite thedownstream end portion of the baffle 15, so that there is, in effect, nodefinite end to that passage.

The passage 38 like-wise has, in effect, an indefinite terminus, owingto the presence of a number of apertures 43 in the baffle 15, near thedischarge end of the tube, which provide for a certain amount ofcommunication between the passages 38 and 39. It has been found thatbest results are obtained when these apertures are elongated lengthwiseof the tube, as shown.

From the foregoing description taken with the accompanying drawings itwill be apparent that this invention provides an exhaust outlet tube fora single cylinder internal combustion engine exhaust system by whichexhaust gases can be discharged in a desired direction and to a desiredlocation without any increase in the noise level of the exhaust systemand without causing undue loss of engine power.

What is claimed as my invention is:

1. An exhaust mufller for an internal combustion engine having acylinder with an exhaust port in a wall thereof, said mufllercomprising:

(A) means defining an expansion chamber having spaced apart first andsecond wall portions,

(1) the first wall portion having an inlet opening therein and beingadapted to be clamped against said wall of the engine cylinder with theinlet opening in registry with the exhaust port of the engine, and

(2) the second wall portion having an outlet opening therein;

(B) baflle means in the expansion chamber defining a plurality oftortuous paths for gases flowing from the inlet opening to the outletopening;

(C) an out let tube;

(D) means mounting the outlet tube on the second wall portion of theexpansion chamber with one end of the tube in registry with the outletopening so that the tube receives exhaust gases from the expansionchamber and determines the direction of their discharge; and

(E) means to silence the discharge of exhaust gases from the tubecomprising:

(1) a baflle in the tube extending lengthwise in its downstream endportion and dividing said portion of the tube into two lengthwiseextending passages, one of which is generally convergent and the otherof which is generally divergent toward the downstream end of the tube,said baflle having apertures in its downstream end portion, and

(2) the wall of the tube having a notch extending in from its dischargeend and at its side that defines said other passage.

2. The exhaust muffler of claim 1, further characterized by:

(A) said first and second wall portions of the expansion chamber beingdisposed at an obtuse angle to one another such that the axes of theinlet and outlet openings diverge outwardly of the expansion chambers;

(B) the outlet tube being medially bent to dispose its end portions atan obtuse angle to one another substantially equal to said angle betweenthe wall portions; and

(C) said means mounting the outlet tube on the second wall portionproviding for adjusting rotation of the upstream end portion of the tubeabout its axis to enable the downstream end portion of the tube to bedisposed in any of a number of different positions, in one of which ithas its axis parallel to that of the inlet opening.

3. The exhaust mufller of claim 1, further characterized by:

said baffie comprising an elongated flat plate having its surfacesoblique to the axis of the downstream portion of the outlet tube.

4. The exhaust mufller of claim 3, further characterized by:

the apertures in said baflle being elongated in the direction lengthwiseof the plate.

5. An exhaust mufller for an internal combustion engine having acylinder with an exhaust port in a wall thereof, said mufllercomprising:

(A) means defining an expansion chamber having (1) an inlet openingadapted to register with an exhaust port in an engine cylinder, and

(2 an outlet opening spaced from the inlet openmg and so oriented thatgases emerging from the expansion chamber therethrough flow in adifferent direction than that in which they entered the inlet opening;

(B) baflle means in the expansion chamber defining a tortuous path forgases flowing therethrough from the inlet-opening to the outlet opening;and

(C) means for directing gases issuing from the outlet opening to a zonespaced therefrom, said means comprising:

(1) an outlet tube bent medially of its ends to dispose its end portionsat an obtuse angle to one another,

(2) means mounting the outlet tube with one of its ends in registry withthe outlet opening,

(3) a substantially rectangular flat baflle plate in the outlet tubewith one of its ends near the other end of the outlet tube, the otherend of the baflle plate being near the bend in the tube and the baflleplate having its surfaces oblique to the axis of the tube portion inwhich it is disposed so as to divide said portion of the tube into apair of passages, one of which generally converges and the other ofwhich generally diverges toward said other end of the tube,

(4) said baflle plate having lengthwise elongated apertures in its firstmentioned end portion, and

(5) said tube having a notch opening to its said other end in the wallportion thereof that defines said other passage, opposite the baflieplate.

6. The exhaust mufller of claim 5 wherein said outlet opening is formedin a substantially flat wall portion of the expansion chamber, furthercharacterized by said 35 means mounting the outlet tube comprising:

(A) a radially outwardly projecting circumferential flange on the outlettube near the first mentioned end thereof, said flange overlying saidwall portion of the expansion chamber;

(B) a substantially flat retaining plate having an aperture thereinthrough which the tube is receivable; and

(C) means releasably securing the retaining plate to the expansionchamber with the retaining plate overlying said flange and said wallportion, said last named means providing for rotational adjustment ofthe outlet tube to dispose its said other end in any of a number ofdifferent positions.

7. An exhaust muffier for an internal combustion engine having acylinder with an exhaust port in a wall thereof, said mufilercomprising:

(A) connected body and cover members forming an expansion chamber with apair of opposite walls,

(1) one of said walls having spaced apart first and second wallportions, the former having an inlet opening therein and the latterhaving an outlet opening therein,

(2) the first wall portion being adapted to be clamped against said wallof the engine cylinder with the inlet opening in registry with theexhaust port of the engine;

(B) baflle means in the expansion chamber dividing the interior thereofinto an inlet compartment to which the inlet opening leads and an outletcompartment from which the outlet opening leads;

(C) an outlet tube; and

(D) means mounting the outlet tube on said second wall portion with oneend of the outlet tube in registry with said opening, so that the tubereceives the exhaust gases leaving the expansion chamber and determinesthe direction of their discharge.

8. The exhaust mufiler of claim 7, wherein said first and second wallportions are disposed at an obtuse angle to one another and wherein saidoutlet tube has a medial bend that disposes its end portions at an angleto one a 7 another substantially equal to said obtuse angle, furthercharacterized by said means mounting the outlet tube comprising:

(A) a crimp in'the outlet tube near said one end thereof defining aradially outwardly projecting flange around the outlet tube;

(B) a retainer having an aperture therein in which the outlet tube isreceivable with a substantially close fit; and

(C) releasable meanssecuring the retainer to the second wall portion inoverlying relation to the latter, for holding the retainer with thecrimp confined between it and the second wall portion, release of saidlast named means enabling the tube to be rotated to dispose its otherend portion in any of a number of positions, in one of which the axisthereof is parallel to the axis of the inlet opening.

9. An exhaust outlet tube for an internal combustion engine exhaustsystem, said outlet tube having an upstream end portion into whichexhaust gases can flow and a downstream end portion from which exhaustgases can be discharged in a desired direction and to a desired zone,said outlet tube being characterized by:

(A) baffle means in the tube cooperating with it to de- (A) said bafliemeans comprising a substantially fiat plate which extends transverselyacross the tube and lengthwise therein at an inclination to the axis ofthe downstream end portion of the tube so that said one passageconverges toward its downstream end and said other passage divergestoward its downstream end; and

(B) the downstream end portion of the tube having a substantially largenotch in the wall portion thereof that defines said other passage,opposite the baffle, whereby the downstream end of said other passage isdisposed a distance in the upstream direction from the downstream end ofthe first designated passage,

11. The exhaust outlet tube of claim 10, further characterized by? e theapertures in the bafile means being elongated in thedirection'lengthwise of the tube.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 354,913 6/ 1922Germany. 410,247 5/ 1934 Great Britain. 475,047 10/ 1952 Italy.

514,686 2/1955 Italy.

ROBERT S. WARD, 1a., Primary Examiner.

